Underwater pelletizer

ABSTRACT

An underwater pelletizer for cutting extruded plastic into a flow of liquid is disclosed. The pelletizer includes a cutter hub ( 90 ) carrying at least one cutter blade ( 96 ), a cutter shaft ( 60 ) for rotationally driving the cutter hub, and a flexible torque converter ( 80 ) for connecting a motor to the cutter hub. In one embodiment, the torque converter has a first set of bushings ( 82 ) that is fastened to a face ( 98 ) of the cutter hub and a second set of bushings that is fastened to a face ( 64 ) of the cutter shaft. The disclosed pelletizer has a shaft extension ( 20 ) configured to engage a motor shaft, the shaft extension having an outer diameter having formed thereon a splined portion ( 38 ) and first ( 26 ) and second ( 28 ) sealing surfaces. A disclosed motor adaptor ( 40 ) has a seal surface ( 44 ). A water chamber plate ( 50 ) may also have a seal surface ( 52 ). A first mechanical seal ( 48 ) is illustratively configured to engage the first seal surface ( 26 ) of the shaft extension and the seal surface ( 44 ) of the motor adaptor. A second mechanical seal ( 49 ) is illustratively configured to engage the second seal surface ( 28 ) of the shaft extension and the seal surface ( 52 ) of the water chamber plate. Furthermore, a cutter shaft ( 60 ) has a splined bore ( 62 ) formed therein for engaging the splined portion ( 38 ) of the shaft extension.

FIELD OF THE INVENTION

This invention pertains to the field of underwater pelletizers, whichare adapted to be mounted to the end of an extruder for cutting streamsof plastic extruded through a die into pellets, which are carried awayby water flow in a water chamber where the cutting takes place.

BACKGROUND OF THE INVENTION

Extruders for extruding plastic material from a molten stream of plasticmaterial have been known and used for some time. One particular use ofsuch an extruder is in connection with a pelletizer assembly, which ismounted to the end of the extruder. In such a combination of an extruderand a pelletizer, a die having a plurality of holes therein is mountedat the end of the extruder and at the entrance to the pelletizerassembly and forms part of both. The pelletizer then includes a rotatingcutter assembly having cutting blades positioned adjacent the die facefrom which streams of molten plastic material flow. The rotating cutterassembly cuts the streams of plastic material into pellets of varioussizes depending upon the extrusion flow rate through the holes in thedie and the speed of rotation of the cutter assembly.

Also, the flow of water through the chamber serves to carry the pelletsaway from the chamber.

In such a combined extruder and pelletizer assembly it is desirable toprovide means for facilitating a smooth flow of the plastic materialfrom the extruder to the die holes in the die. Also it is desirable toprovide means for gaining easy access to the chamber for servicing thepelletizer, such as to replace worn cutting blades of the cutterassembly, to generally observe the formation of pellets by the rotatingcutter assembly, and to clean the die.

It is also desirable to provide a long useful life for the cuttingblades of the cutter assembly and die. That is to say, it is desirableto provide cutting blades that will last a long time. In addition, it isdesirable to provide some means for automatically readjusting theposition of the cutter assembly adjacent the die face as the spacebetween the cutter assembly and the die face increases due to wear ofthe cutting blades. In this respect, it is desirable to keep the cuttingblades juxtaposed to the die face to ensure clean cutting of the streamsof plastic material into pellets.

U.S. Pat. No. 4,529,370 illustrates one example of a conventionalunderwater pelletizer.

Another example of a conventional underwater pelletizer is shown in U.S.Pat. No. 5,059,103. Some conventional components for pelletizers areshown in U.S. Pat. Nos. 4,621,996; 5,403,176; 5,624,688; and 6,332,765.

BRIEF SUMMARY OF THE INVENTION

An embodiment of an underwater pelletizer includes a flexible torqueconverter disc that engages a cutter hub having cutting blades and acutter drive hub that is driven by a motor. The flexible torqueconverter disc accommodates misalignment between a motor shaft and a dieface and maintains the cutting blades in contact with a die face duringrotation. In a further refinement, mechanical seals are provided for ashaft extension to pass through a motor adaptor and a water chamberplate and provide for a high-pressure chamber. An access hole and a borethrough the shaft extension permit a hub piston to be controlled byvarying the pressure in the high pressure chamber in order to controlthe pressure of the cutting hub against the die face. In still anotherrefinement, the water chamber has a water inlet and outlet arranged sothat water pumped into the water chamber forms a vortex that rotates inthe same direction as the rotation of the cutter hub. In a furtherrefinement of this embodiment, the water chamber is fixedly attached tothe motor adaptor and removably coupled to the die.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment is described below with respect to the followingdrawings, wherein:

FIG. 1 is an exploded view showing individual components of anembodiment of a pelletizer with an automatic water chamber clamp;

FIG. 2 is a front view of the cutting hub of FIG. 1;

FIG. 3 is a side view of the cutting hub of FIG. 1;

FIG. 4 is a top view of the cutting blade of FIGS. 1-3;

FIG. 5 is an isometric view of the cutting blade of FIGS. 1-4;

FIG. 6 is an assembled side view illustrating the water chamber housingof FIG. 1 and associated water circulation equipment;

FIG. 7 is an assembled cross-sectional view of the underwater pelletizerof FIGS. 1 and 6 that also illustrates automated clamping and pressureactuation components;

FIG. 8 is an exploded side view of the components of a cutter shaftassembly that includes a motor shaft extension, cutter shaft, hubpiston, flexible disc coupling and cutter hub;

FIG. 9 is a frontal view of one embodiment of a flexible disc havingfour bushings and FIG. 10 is a side view of the same embodiment;

FIGS. 11 and 12 are side and frontal views, respectively, of anembodiment of a cutter shaft;

FIGS. 13 and 14 are side and frontal views, respectively, of anembodiment of a shaft extension;

FIGS. 15, 16 and 17 are rear, side and frontal views, respectively, ofan eight bladed embodiment of a cutter hub;

FIG. 18 is a side view of an embodiment of a piston for a diverter valvewith grooves formed on a periphery of the piston.

DETAILED DESCRIPTION OF THE INVENTION

It is desirable to maintain the cutting blades of an underwaterpelletizer in contact with a die face of an extrusion die in order toproduce pellets of relatively uniform size and shape, as well as toavoid jamming the cutting blades with extruded plastic.

One conventional cutting blade configuration present in devices producedby Gala Industries, Inc., includes a self-aligning cutting bladeassembly that attaches to a motor shaft through a spherical coupling.The spherical coupling consists of a cut-away ball joint that isthreaded for connection to a motor shaft. A pair of ball bearings andassociated traces are used to implement a floating connection betweenthe spherical coupling and the rest of the cutting blade assembly.

As the shaft rotates about a rotational axis, the spherical couplingpermits the cutting blade assembly to float, e.g. move with respect tothe rotational axis, in order to compensate for misalignment between theshaft and the die. The movement of the spherical coupling maintains thecutting blades in contact with the die face. However, the sphericalcoupling is used to transmit axial force for forcing the cutting bladeassembly against the die face and radial force for rotating the cuttingblade assembly using the motor shaft. Consequently, a large amount offorce is focused on the ball bearing traces and they are prone to rapidwearing.

It is also desirable to provide for rapid cleaning of the cuttingblades, die and water chamber, which must be cleared of excess extrudedplastic in order to operate properly. Conventional underwaterpelletizers provide for the plastic to be extruded through holes in thedie face into a water chamber, where the plastic is cut by the cuttingassembly. During start-up procedure the water chamber is flooded withplastic and it has to be manually removed by the operator. The waterchamber is typically fixedly attached to the die and a motor adaptorwith a water seal is removably coupled to the other end of the waterchamber.

The water seals provided in conventional underwater pelletizers aretypically oil seals, which tend to break down if subjected tosignificant levels of water pressure. Breakdown of the seals leads towater entering the motor assembly, which can damage the motor andrequires replacement of the seals.

Conventional water chambers have a water intake on one side of thechamber, e.g. the bottom, for inflow of water and an outlet on anotherside, e.g. the top, for outflow of water and pelletized material. Theresulting flow of material is in one direction through the chamber. Thecutting blade assembly rotates within the water chamber in approximatelythe same plain as the vector of the water flow through the chamber.Consequently, the blades of the cutting blade assembly rotatesubstantially with the water flow through half their rotation andagainst the water flow through the other half of their rotation. As aresult, a significant amount of power is required to drive the cuttingblade assembly against the flow of water in the water chamber.

Conventional blades used in conventional cutting blade assembliestypically have two sharpened cutting edges that engage the die face forcutting plastic as it is extruded. These blades are sharpened onopposing edges of a body of the blade, where the cutting edge is formedon opposing planar sides of the body so that the blade can be removedand reversed when one cutting edge has worn out. The conventional bladestypically have two bolt holes for bolting the blade into the cuttingblade assembly so that the blade does not rotate out of position underload when the cutting blade assembly is engaged and rotated against thedie face. The conventional blades wear out after the two cutting edgesare used up.

FIG. 1 is an exploded view of an exemplary embodiment of an improvedunderwater pelletizer. A motor 10 has a shaft 12 that engages shaftextension 20. The shaft extension 20 passes through a motor adaptor 40and water chamber plate 50 to engage cutter shaft 60. A dual mechanicalshaft seal assembly 48 is used to provide a seal between the shaftextension 20 and motor adaptor 40 at both a motor side and a waterchamber plate side. Another mechanical seal engages water chamber plate50 and provides a seal for shaft extension 20 between motor adaptor 40and water chamber plate 50. Shaft extension 20 also engages hub piston70, which engages pressure plate 92 of cutter hub 90.

Water chamber housing 100 has a first open end 102 that is coupled towater chamber plate 50 such that cutter shaft 60 and cutter hub 90 aredisposed within water chamber bore 104. A second open end 106 of waterchamber housing 100 is adapted to engage die ring 130 and driven rotor140 removably couples thru the set of eccentrically guided pins withradial bearings water chamber housing 100 to die 150. Die 150 is fixedlyconnected to die ring 130 on one side and to die clamp adaptor 160 onthe other side, which engages clamp 180 for clamping die 150 to divertervalve 190. Flow distributing insert 170 facilitates annular flow ofplastic from diverter valve 190 to die 150, where the plastic isextruded through holes in die face 152.

The shaft extension 20 has a first bore 22 for engaging shaft 12 ofmotor 10. A seal surface 26 is provided for seating a first mechanicalshaft seal 48 against seal surface 44 of motor adaptor 40. Another sealsurface 28 is provided for seating second mechanical shaft seal 49against seal surface 52 of water chamber plate 50. When shaft extension20 is assembled with motor adaptor 30 and water chamber plate 50 withmechanical shaft seals 48 and 49, a high-pressure chamber 42 is formedwith motor adaptor 40 and water chamber plate 50, where the pressure inthe high pressure chamber 42 may be controlled via pressure regulator250 illustrated in FIG. 7.

Shaft extension 20 also includes piston chamber 32 for receiving hubpiston 70. Piston chamber 32 is in communication with pressure accesshole 36 via axial bore 34. When assembled, pressure access hole 36 is incommunication with high-pressure chamber 42 of motor adaptor 40 and hubpiston 70 is seated in piston chamber 32. Consequently, the axial forceapplied to pressure plate 92 of cutter hub 90 by hub piston 70 may becontrolled by varying the pressure in high-pressure chamber 42 viapressure regulator 250 attached to pressure port 46, as illustrated inFIG. 7. Thus, the axial pressure of cutter hub 90 against die face 152is externally controllable during operation of the pelletizer.

Motor shaft extension 20 has a splined outer surface region 38 that,when assembled, engages splined bore 62 of cutter shaft 60. Cutter shaft60 has a flexible disc engagement face 64 that is formed to engagebushings 82 of flexible torque transmitting disc 80. Cutter hub 90 alsohas a disc engagement face 98 that is formed to engage bushings 82 offlexible torque transmitting disc 80. When assembled, rotary forcegenerated by shaft 12 of motor 10 is transmitted through shaft extension20 to cutter shaft 60 and from cutter shaft 60 through flexible torquetransmitting disc 80 to cutter hub 90 in order to rotate the cutterblades 96 against die face 152 of die 150.

Flexible torque transmitting disc 80 is a standard torque-transmittingdevice that is a generally available power transmission productfrequently used in other power transmission applications. In the presentembodiment, disc 80 is constructed of laminated sheets of stainlesssteel that permits approximately 5° of movement. The stainless steelprevents disc 80 from corroding due to contact with water in waterchamber housing 100. The flexibility of disc 80 permits it toaccommodate both angular and parallel misalignment between motor shaft12 and die 150. Disc 80 transmits only rotary force from cutter shaft 60to cutter hub 90 and transmits no axial force necessary to keep theblades 96 attached to the cutter hub 90 against die face 152.

Note that the cutter hub 90, cutter shaft 60, blades 96, flexible disc80 and die 150 arrangement operates to maintain substantially consistentpressure of the blades against the die face 152. This results in blades96 self-sharpening as they rotate against the die face 152. By avoidinguneven wear of the die face 152, the present arrangement can extend theoperational life of the die 150.

As shown in FIG. 1, water chamber housing 100 has a water inlet opening110, a water outlet opening 112, and a drain outlet 114. The water inlet110 and water outlet 112 are formed in the water chamber housing suchthat they are substantially parallel and adjacent to one another. Whenthe pelletizer is assembled, the water inlet 110 and outlet 112 arearranged with respect to the rotation of cutter hub 90 so that a watervortex is formed within water chamber housing 100 that rotates in thesame direction as cutter hub 90. The resulting arrangement substantiallyreduces the amount of power required to rotate cutter hub 90 whilecutting extruded plastic. It also results in improved pellet removal andreduces jamming.

In the pelletizer of FIG. 1, water chamber housing 100 is fixedlyattached, e.g. bolted, to water chamber plate 50, which is connected tomotor adaptor 40. In this embodiment, water chamber housing 100 isformed with an automatic clamp fitting for engaging die ring 130 via anautomatic clamp rotor 140, which is discussed in further detail belowwith regard to FIG. 7. When the pelletizer is assembled, water chamberhousing 100 is fixedly attached to motor 10 and removably coupled to thedie ring 130 and the die 150 via a clamping mechanism.

If an automated clamp mechanism is used in conjunction with a meltdiverting valve and automatic water bypass system, then the start-up andshut-down process for the pelletizer can be fully automated. Thisarrangement substantially improves system efficiency and operator safetyover manual procedure.

The embodiment of FIG. 1 includes a die clamp adaptor 160 for fixedattachment to die 150. The die 150 is then removably coupled to divertervalve 190 via quick clamp 180. This arrangement permits that both thefront and back of die 150 are rapidly accessible for maintenance andcleaning.

FIGS. 2 and 3 show an exemplary embodiment of cutter hub 90 of FIG. 1.FIG. 2 is a front view of the cutter hub from the perspective of the dieface 152 that faces hub lid 94. FIG. 3 is a side view of the cutter hub.Cutter hub 90 includes multiple cutter blades 96A-D arranged along aperiphery of the cutter hub 90 and secured within slots formed inhousing 210, e.g. slot 214C shown in FIG. 3. The slots are formed inhousing 210 of cutter hub, and are wide enough to receive and holdsecurely a center portion 220 (shown in FIGS. 4 and 5) of each cuttingblade 96. FIG. 3 shows slot 214C for mounting one of the blades 96C ofFIG. 2. A drilled and tapped bore 212C is formed into housing 210 of hub90 for insertion, in this example, of a conical tip set screw 216C foraligning and securing blade 96C within the housing 210 through screwhole 224 in the blade.

FIGS. 4 and 5 show an exemplary embodiment of cutting blades 96A-D. Eachcutting blade 96 is substantially symmetrical along two perpendicularaxes A and B. A central portion 220 of cutting blade 96 is positionedalong axis B and has a substantially rectangular cross-section forholding the blade securely within slot 214 in the cutting hub housing210. Each cutting blade has up to four cutting edges 222A-D formed intoit, where the cutting edges are formed proximally from the centralportion and perpendicular to axis A. The cutting edges 222A-D are formedon two opposing surfaces X and Y of blade 96. Diametrically opposedcutting edges are formed on the same surface. For example, edges 222Aand 222C are formed on planar surface Y and edges 222B and 222D areformed on planar surface X. The resulting cutting blade 96 may beremoved from cutter hub 90 and rotated so that all four edges 222A-D maybe used for cutting before blade 96 is worn out. Removing and rotatingblade 96 is accomplished by backing out set screw 216, rotating and/orreversing blade 96, and resetting set screw 216.

In a preferred embodiment, a single securing hole 224 is formed at theintersection of axes A and B of blade 96. The securing hole 224 isadapted to engage set screw 216 threaded through bore 212 in the cutterhub housing 210 that holds the cutting blade securely in place withincutter hub 90. This arrangement results in the cutting blade beingself-aligning within cutter hub 90. The conical tip of set screw 216,along with the alignment of screw hole 224 and bore hole 212 combine toalign blade 96 within the housing 210.

FIG. 6 is an assembled side view illustrating the water chamber housing100 of FIG. 1 fixedly coupled to motor adaptor 40 and motor 10 alongwith associated water circulation ports. Flow sight 230, which allowswater and pelletized material to be observed leaving water chamberhousing 100, is coupled to water outlet 112 via cam and groove coupling236 and on top is coupled to hose fitting 232 via cam and groovecoupling 234, where hose fitting receives a water and pellet hosetypically for transporting the resulting pelletized material to a pelletdryer. Water inlet 110 is coupled to hose fitting 238 via cam and groovecoupling 237, where hose fitting 238 receives a water supply line.Pneumatic valve 240 is coupled to drain outlet 114 and has a hosefitting 242 for receiving a hose for draining water chamber housing 100.

FIG. 7 is an assembled cross-sectional view of the underwater pelletizerof FIGS. 1 and 6 that also illustrates automated clamping and pressureactuation components. Motor 10 is secured to motor adaptor 40, which issecured to water chamber plate 50. Shaft extension 20 is coupled tomotor shaft 12 and extends through high pressure chamber 42 formedwithin motor adaptor 40 along with shaft extension 20 and water chamberplate 50. Mechanical shaft seal 48 forms a high pressure seal betweenshaft extension 20 and motor adaptor 40. Mechanical shaft seal 49 formsa high pressure seal between shaft extension 20 and water chamber plate50. In one example, mechanical shaft seals 48 and 49 are ceramic andgraphite disc seals actuated by a stainless steel spring, which arewidely used in other equipment applications.

A pressure regulator 250 (manual or electronic) is connected to supplyport 46 and regulates the pressure in high-pressure chamber 42. Thepressure in high-pressure chamber 42, in turn, affects the amount offorce applied by hub piston 70 to pressure plate 92 of cutting hub 90via pressure access hole 36 and axial bore 34. By controlling thepressure in high pressure air chamber 42, the amount of axial forceapplied by hub piston 70 to cutting hub 90 is controlled duringpelletizer operation or blade lapping sequence.

Shaft extension 20 passes through water chamber plate 50 into waterchamber 101 formed by water chamber housing 100. Cutter shaft 60 isfitted onto shaft extension 20 and is coupled to cutting hub 90 throughflexible disc 80. The blades 96 of cutting hub 90 are pressed againstthe face of extrusion die 150 by hub piston 70. When motor shaft 12rotates, shaft extension 20 also rotates causing cutter shaft 60,flexible disc 80 and cutting hub 90 to rotate in order to cut plasticextruded through holes in die 150.

In the embodiment of FIG. 7, clamp 180 is a hinged quick clamp forengaging die clamp adaptor 160, which is fastened to die 150, and aclamp flange 192 of diverter valve 190. An actuator 300 has a driveshaft 302 for rotationally driving driven gear 304. Driven gear 304engages rotor 140 fastened to water chamber housing 100 in order to openor close water chamber 101. By automatically controlling actuator 300,pressure regulator 250, melt diverter valve 190 and a water bypasssystem start-up and shut-down of the pelletizer can be fully automated.

The water bypass system noted above diverts water from a hose connectedto hose attachment 238 for water inlet 110 shown in FIG. 6 to a hoseconnected to hose attachment 232 connected to water outlet 112. Thisarrangement permits water chamber 100 to be automatically drained duringa shut-down operation, but maintain the inertial flow of water in awater circulation system that attaches to hose attachments 232 and 238.This allows the time required to service an interruption of operation tobe reduced.

FIG. 8 is an exploded side view of the components of a cutter shaftassembly that includes shaft extension 20, cutter shaft 60, hub piston70, flexible disc 80 and cutter hub 90. This expanded view illustrateso-rings 72 and 74 on hub piston 70, which form a seal between hub piston70 and piston chamber 32 of shaft extension 20. As the pressure withinhigh-pressure chamber 42 of FIG. 7 is varied, hub piston 70 moves withinpiston chamber 32. A retainer ring 76 seats into an end of shaftextension 20 and prevents hub piston 70 from being ejected from pistonchamber 32.

Also shown in FIG. 8 are fasteners 84A-C for securing flexible hub 80 tocutter shaft 60 and cutting hub 90. In the embodiment shown, a pair offasteners 84A and 84C secure disc 80 to drive shaft 60. Another pair offasteners, fastener 84B and where the other fastener is obscured fromview by fastener 84B, secures disc 80 to cutting hub 90. The fastenersare inserted through bushings on flexible disc 80 in an alternatingfashion such that each pair of adjacent bushings on flexible disc 80 issecured to a different one of cutter shaft 60 and cutting hub 90. Thisarrangement permits the disc to flex in order to accommodatemisalignment between cutter shaft 60 and cutting hub 90.

FIG. 8 also shows a retainer ring 66 that secures pressure plate 92 tocutter hub 90.

FIG. 9 is a frontal view of one embodiment of flexible disc 80 havingfour bushings 82A-D and FIG. 10 is a side view of the same embodiment.As an example of securing flexible disc 80 in an alternating fashion,bushings 82A and 82C are secured to cutter shaft 60 and bushings 82B and82D are coupled to cutter hub 90. Other arrangements are possible, asare other embodiments where there are a larger number of bushingsutilized.

FIGS. 11 and 12 are side and frontal views, respectively, of anembodiment of cutter shaft 60. Note that disc engagement face 64 that isformed to engage bushings 82 of flexible torque transmitting disc 80includes, in one exemplary embodiment, threaded bores 362A and 362B forreceiving fasteners 84A and 84C of FIG. 8 for securing bushings 82A and82C of flexible disc 80 to cutter shaft 60. Also note recesses 364A and364B, which accommodate fastener 84B and another fastener that isobscured in FIG. 8 for securing bushings 82B and 82D to cutting hub 90.Note that recesses 364A and 364B are preferably sized larger than theheads of fastener 84B to allow for flexion in disc 80. Further note inFIG. 12 the splined surface 366 of splined bore 62 for receiving splinedouter surface region 38 of shaft extension 20 shown in FIG. 14.

FIGS. 13 and 14 are side and frontal views, respectively, of anembodiment of shaft extension 20. As noted above, piston chamber 32 isin communication with pressure access hole 36 via axial bore 34 so that,when assembled, pressure access hole 36 is in communication withhigh-pressure chamber 42 of motor adaptor 40 shown in FIG. 7. Shaftextension 20 has a splined outer surface region 38 that, when assembled,engages splined bore 62 of cutter shaft 60.

Piston chamber 32 is in communication with pressure access hole 36 viaaxial bore 34, as further illustrated in FIG. 7. When assembled, asillustrated in FIG. 7, pressure access hole 36 is in communication withhigh-pressure chamber 42 of motor adaptor 40 and hub piston 70 is seatedin piston chamber 32. Consequently, the axial force applied to pressureplate 92 of cutter hub 90 by hub piston 70 may be controlled by varyingthe pressure in high-pressure chamber 42 via pressure supply port 46.Thus, the axial pressure of cutter hub 90 against die face 152 isdynamically controllable during operation of the pelletizer or bladelapping sequence. p As shown in FIG. 14, shaft extension 20 has asplined outer surface region 38 that, when assembled, engages splinedbore 62 of cutter shaft 60, shown in FIG. 12. The splines of splinedbore 62 may be formed by gear cutting or honing the interior surface ofbore 62, which results in a robust engagement of the shaft extension 20to cutter shaft 60. Seal surface 26, shown in FIGS. 13 and 14, isprovided for seating a mechanical shaft seal 48 against seal surface 44of motor adaptor 40, shown in FIG. 1. Another seal surface 28, shown inFIG. 13, is provided for engaging second mechanical shaft seal againstseal surface 52 of water chamber plate 50, shown in FIG. 1.

FIGS. 15, 16 and 17 are rear, side and frontal views, respectively, ofan eight bladed embodiment of a cutter hub 90B. FIG. 14 shows a discengagement face 398 that is formed to engage bushings 82 of flexibletorque transmitting disc 80. In this embodiment, disc engagement faceincludes threaded bores 392A and 392B for receiving fastener 84B andanother fastener that is obscured in FIG. 8 for securing bushings 82Band 82D to cutting hub 90. Also note recesses 394A and 394B, whichaccommodate fasteners 84A and 84C of FIG. 8 for securing bushings 82Aand 82C of flexible disc 80 to cutter shaft 60. Note that recesses 394Aand 394B are preferably sized larger than the heads of fasteners 84A and84C to allow for flexion in disc 80.

Further note slot 414A formed in the body of hub 390 for receiving acutting blade, such as those discussed above. A threaded bore 412A isformed at an angle and intersects slot 414A so that a set screw can beused to secure the cutting blade in place within slot 414A. Note thatother configurations for cutter hub are possible, such as a six bladedembodiment.

In one embodiment, the diverter valve 190 shown in FIGS. 1 and 6 has apiston 194 with peripheral grooves formed thereon, as shown in FIG. 18.In this embodiment, the grooves are approximately ⅛ of an inch wide anddeep. Because the diverter valve piston 194 is typically subject totight tolerances, e.g. thousandths of an inch, with the diverter valvehousing 190, the piston 194 is vulnerable to jamming due to contaminantparticles, such as metal filings or wood splinters, that tend to jamconventional pistons. In this embodiment, the peripheral grooves trapthe contaminant particles to prevent the particles from jamming thepiston 194. Also, molten plastic within the diverter valve 190 tends tosolidify within the grooves and helps form a seal between the piston 194and the diverter valve 190.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Recitation of ranges of values herein are merely intended toserve as a shorthand method of referring individually to each separatevalue falling within the range, unless otherwise indicated herein, andeach separate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the invention and does not pose alimitation on the scope of the invention unless otherwise claimed. Nolanguage in the specification should be construed as indicating anynon-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention. Itshould be understood that the illustrated embodiments are exemplaryonly, and should not be taken as limiting the scope of the invention

1. An underwater pelletizer for cutting extruded plastic into a flow ofliquid, the pelletizer comprising: a cutter hub (90) carrying at leastone cutter blade (96); a cutter shaft (60) for rotationally driving thecutter hub; and a flexible torque converter (80) for connecting a motorto the cutter hub, the torque converter having a first set of bushings(82) that are fastened to a face (98) of the cutter hub and a second setof bushings that are fastened to a face (64) of the cutter shaft.
 2. Theunderwater pelletizer of claim 1, wherein: the cutter hub includes afirst set of recesses (392) formed in the face (98) of the cutter hub(90), each recess of the first set of recesses being configured toaccommodate one of the first set of bushings (82) and permit the one ofthe first set of bushings to be fastened to the cutter hub, and a secondset of recesses (394) each recess of the second set of recesses beingconfigured to accommodate one of the second set of bushings; and thecutter shaft (60) includes a first set of recesses (362) formed in theface (64) of the cutter shaft, each recess of the first set of recessesbeing configured to accommodate one of the first set of bushings (82),and a second set of recesses (396) each recess of the second set ofrecesses being configured to accommodate one of the second set ofbushings and permit the one of the second set of bushings to be fastenedto the cutter shaft.
 3. The underwater pelletizer of claim 2, wherein:the cutter hub (90) includes a set of threaded holes formed in the firstset of recesses of the cutter hub, each threaded hole configured toreceive a fastener inserted through an aperture in one of the first setof bushings; and the cutter shaft (60) includes a set of threaded holesformed in the second set of recesses of the cutter shaft, each threadedhole configured to receive a fastener inserted through an aperture inone of the second set of bushings.
 4. The underwater pelletizer of claim1, the pelletizer including: a shaft extension (20) configured to engagea motor shaft, the shaft extension having an outer diameter havingformed thereon a splined portion (38) for engaging the cutter shaft andfirst (26) and second (28) sealing surfaces; a motor adaptor (40) havinga seal surface (44); a water chamber plate (50) having a seal surface(52); a first mechanical seal (48) configured to engage the first sealsurface (26) of the shaft extension and the seal surface (44) of themotor adaptor; a second mechanical seal (49) configured to engage thesecond seal surface (28) of the shaft extension and the seal surface(52) of the water chamber plate; and the cutter shaft (60) has a splinedbore (62) formed therein for engaging the splined portion (38) of theshaft extension.
 5. The underwater pelletizer of claim 4, wherein: theshaft extension (20), the motor adaptor (40), the water chamber plate(50) and the first and second mechanical seals (48, 49) form a highpressure chamber (42) when assembled; and the shaft extension has formedtherein a piston chamber (32), an axial bore (34) 20 in communicationwith the piston chamber, and a pressure access hole (36) incommunication with the axial bore and the high pressure chamber; and thepelletizer further includes a hub piston (70) disposed in the pistonchamber (32) and configured to apply pressure against the cutter hub(90).
 6. The underwater pelletizer of claim 5, where the motor adaptor(40) has formed therein a pressure port (46) in communication with thehigh pressure chamber (42) and the pelletizer further includes apressure regulator (250) coupled to the pressure port for controllingthe pressure within the high pressure chamber.
 7. The underwaterpelletizer of claim 6, where the hub piston (70) is pneumaticallycontrolled by the pressure regulator (250).
 8. The underwater pelletizerof claim 6, where the hub piston (70) is hydraulically controlled by thepressure regulator (250).
 9. The underwater pelletizer of claim 1, thepelletizer further comprising a water chamber housing (100) havingformed therein a water inlet (110) and a water outlet (112), the waterchamber housing being fixedly attached to the water chamber plate (50),where the water inlet and water outlet are positioned so that duringoperation a water vortex is formed within the water chamber housing thatrotates in a same rotational direction as the cutter hub (90).
 10. Theunderwater pelletizer of claim 9, wherein the water inlet (110) and thewater outlet (112) are positioned substantially parallel and adjacent toone another.
 11. The underwater pelletizer of claim 9, wherein the shaftextension (20) rotates on a rotational axis and the water inlet andwater outlet are positioned at points offset from the rotational axis.12. The underwater pelletizer of claim 9, wherein the pelletizer furtherincludes: a die (150) for extruding plastic; a die ring (130) fixedlyattached to the die; the water chamber housing further includes anautomatic clamp fitting for engaging the die ring; and an automaticclamp rotor (140) for clamping the die to the automatic clamp fitting ofthe water chamber housing.
 13. The underwater pelletizer of claim 9, thewater chamber housing (100) having formed therein a drain outlet (114),the pelletizer further comprising a valve (240) coupled to the drainoutlet (114) and has a hose fitting (242) for receiving a hose fordraining the water chamber housing (100).
 14. The underwater pelletizerof claim 13, the pelletizer further including a first hose fitting (238)coupled to water inlet (110) and a second hose fitting (232) coupled tothe water outlet (114) and further including a bypass disposed betweenthe first and second hose fittings for diverting water flow from thewater chamber housing (100).
 15. The underwater pelletizer of claim 1,wherein: the at least one cutting blade (96) has a center portion (220)with a hole (224) formed therein; and the cutter hub has a peripherywith, for each cutting blade, a slot formed therein for securing thecenter portion of the cutting blade, and the cutter hub has furtherformed therein a tapped bore that intersects the slot for accommodatinga set screw and, when assembled, the set 10 screw engages the holeformed in the cutting blade so that the set screw aligns the cuttingblade.
 16. The underwater pelletizer of claim 15, where the at least onecutting blade (96) has formed thereon four cutting edges (222A-D)proximate to the center portion, where the at least one cutting blademay be removed from the cutting hub and reinserted and secured in thecutting hub so that all four cutting edges may be used.
 17. Anunderwater pelletizer for cutting extruded plastic into a flow ofliquid, the pelletizer comprising: a shaft extension (20) configured toengage a motor shaft, the shaft extension 20 having an outer diameterhaving formed thereon a splined portion (38) and first (26) and second(28) sealing surfaces; a motor adaptor (40) having a seal surface (44);a water chamber plate (50) having a seal surface (52); a firstmechanical seal (48) configured to engage the first seal surface (26) ofthe 25 shaft extension and the seal surface (44) of the motor adaptor; asecond mechanical seal (49) configured to engage the second seal surface(28) of the shaft extension and the seal surface (52) of the waterchamber plate; and a cutter shaft (60) having a splined bore (62) formedtherein for engaging the splined portion (38) of the shaft extension.18. The underwater pelletizer of claim 17, wherein: the shaft extension(20), the motor adaptor (40), the water chamber plate (50) and the firstand second mechanical seals (48, 49) form a high pressure chamber (42)when assembled; and the shaft extension has formed therein a pistonchamber (32), an axial bore (34) 5 in communication with the pistonchamber, and a pressure access hole (36) in communication with the axialbore and the high pressure chamber; and the pelletizer further includesa hub piston (70) disposed in the piston chamber (32) and configured toapply pressure against a cutter hub (90).
 19. The underwater pelletizerof claim 18, where the motor adaptor (40) has formed therein a pressureport (46) in communication with the high pressure chamber (42) and thepelletizer further includes a pressure regulator (250) coupled to thepressure port for controlling the pressure within the high pressurechamber.
 20. The underwater pelletizer of claim 19, where the hub piston(70) is pneumatically controlled by the pressure regulator (250). 21.The underwater pelletizer of claim 9, where the hub piston (70) ishydraulically controlled by the pressure regulator (250).
 22. Theunderwater pelletizer of claim 17, the pelletizer further comprising awater chamber housing (100) having formed therein a water inlet (110)and a water outlet (112), the water chamber housing being fixedlyattached to the water chamber plate (50), where the water inlet andwater outlet are positioned so that during operation a water vortex isformed within the water chamber housing that rotates in a samerotational direction as the cutter hub (90).
 23. The underwaterpelletizer of claim 22, wherein the water inlet (110) and the wateroutlet (112) are positioned substantially parallel and adjacent to oneanother.
 24. The underwater pelletizer of claim 22, wherein the shaftextension (20) rotates on a rotational axis and the water inlet andwater outlet are positioned at points offset from the rotational axis.25. The underwater pelletizer of claim 22, wherein the pelletizerfurther includes: a die (150) for extruding plastic; a die ring (130)fixedly attached to the die; the water chamber housing further includesan automatic clamp fitting for engaging the die ring; and an automaticclamp rotor (140) for clamping the die to the automatic clamp fitting ofthe water chamber housing.
 26. The underwater pelletizer of claim 22,the water chamber housing (100) having formed therein a drain outlet(114), the pelletizer further comprising a valve (240) coupled to thedrain outlet (114) and has a hose fitting (242) for receiving a hose fordraining the water chamber housing (100).
 27. An extruder for extrudingplastic into a flow of liquid, the extruder comprising: a motor (10)having a motor shaft (12), a cutter hub (90) carrying a cutter blade(96), a torque converter (80) for connecting the motor (10) to thecutter hub (90), and a plurality of bushings (64, 82) coupled to thetorque converter (80) accommodating misalignment between the motor shaft(12) and the cutter hub (90).
 28. The extruder of claim 27, furthercomprising a plurality of recesses (392) formed in a face (98) of thecutter hub (90), each recess (392) being configured to receive a bushing(82).
 29. The extruder of claim 28, further comprising a fastenerconfigured to be inserted through an aperture in one of the bushings.30. The extruder of claim 27, said bushings allow for misalignmentbetween the motor shaft and the cutter hub up to a pre-selected numberof degrees of rotation.
 31. The extruder of claim 27, further comprisinga piston (70) connected to the cutter hub (90).
 32. The extruder ofclaim 31, wherein the piston (70) is a hydraulic piston.
 33. Theextruder of claim 32, further comprising a pressurized fluid chamber(42) for containing pressurized fluid used to control the hydraulicpiston.
 34. The extruder of claim 33, wherein the piston (70) defines anaxis and the pressurized fluid chamber is positioned along the axis ofthe piston.
 35. The extruder of claim 33, further comprising amechanical seal (48) for sealing the pressurized fluid chamber.
 36. Theextruder of claim 31, wherein the piston (70) is configured to move thecutter hub (90) toward and away from a cutter die (150).
 37. Theextruder of claim 27, further comprising a liquid chamber (100)configured to contain the liquid.
 38. The extruder of claim 37, whereinthe liquid is water.
 39. The extruder of claim 37, wherein the liquidchamber (100) has an inlet (110) and an outlet (112).
 40. The extruderof claim 39, wherein the outlet (112) is positioned on a portion of theliquid chamber (100) that is vertically disposed above the motor shaft(12).
 41. The extruder of claim 40, wherein the motor shaft (12) definesa vertical axis, and the inlet (110) and outlet (112) are positioned atpoints offset from the vertical axis.
 42. The extruder of claim 27,further comprising a quick-release clamp (180) configured to provideselectable access to the cutter hub (90).
 43. The extruder of claim 27,wherein the cutter blade (96) comprises four cutting surfaces.
 44. Theextruder of claim 43, further comprising a set screw for engaging andpositioning the cutter blade (96) on the cutter hub (90).
 45. Theextruder of claim 44, further comprising an aperture formed in thecutter blade (96), the aperture being configured to receive the setscrew.